When do we cry? We cry when we are sad, angry, or overwhelmed with joy.But did you know that humans are the only species that shed tears linked to emotions?Many animals make sounds when they cry to signal stress or distress, but they lack the neurological system to produce emotionally driven tears.While scientists understand the mechanics of tear production, the exact reason why humans cry in response to emotions remains a subject of ongoing research.What causes tears?Dr. Marie Bannier-Hélaouët, a postdoctoral fellow at the Institute of Human Biology in Switzerland, explains, 'Tears are composed of five elements: mucus, electrolytes, water,...